Heat staking as a means of locking parts together is well known and has been used for years in a variety of applications including the assembly of parts for the toy industry, the medical industry, and the electronic industry. In general, one of the parts to be assembled is designed to include a plastic post or tab which can be inserted through a hole or aperture in another part and then permanently and inelastically deformed by the generation or application of heat by some tool surface which effects plastic deformation. The variables which must be dealt with include the characteristics of the particular plastic material employed including its flow and melt temperatures, the nature and characteristics of the tooling employed and the geometries thereof, means by which the tooling may be brought to bear against the plastic elements to be deformed, the choice of method for effecting heating, and the parameters of pressure, time, and heat energy applied.
With respect to the assembly of components such as electrical connectors or housings and particularly with respect to mounting such components on printed circuit boards, the concept of heat staking has become more important with the advent of what is known as "surface mounting technology" or SMT as a means of effecting solder or solder-like joints between the contacts of such components and the circuit traces of the printed circuit boards. The surface bonds of contacts and circuit traces by solder is more demanding of the housing structure in relation to strains and stresses which is minimized by securing the housings to the boards independently of such bonds. To this end, one solution has been to secure the housings to a board by screws, pop rivets, or the like. The problem with such techniques is essentially one of economics wherein the ears or wings or brackets added to housings take up board space which is frequently quite expensive, require extra parts in the form of such rivets or the like, and require the labor of assembly which is not easily automated.
As a further aspect of the background of the invention, there is an increasing density of electrical interconnection being employed in the electronic industry which makes it very difficult to provide space within the outline of a given connector for adding mounting means such as rivets or the like.
As a further part of the background of the invention, many assemblies including assemblies of electronic components to printed circuit boards or similar structures, contain components of housings of different plastic materials having different flow and melt characteristics, creating a problem which has heretofore been generally answered by having multiple sets of tooling and different times of cycle which are costly in both capital and labor.
Finally, in the general field of heat staking, problems have been encountered with the buildup of heat which if not dealt with by special cooling techniques, can damage the components which are being heat staked, create unacceptable environments for operator or machine, and, in general, utilize many, many times the energy really necessary to effect heat staking, thereby creating an unpleasant inefficiency.